Method of forming a shell for a spark-plug.



W. E. SHERBONDY. METHOD OF FORMING A SHELL FOR A SPARK PLUG.

APPLICATION FILED DEC.'22 l9l3.

1,152,982. Patentedsept. 7, 1915.

2 SHEETS-SHEET l.

W. E. SHERBONDY.

METHOD OF FORMING A SHELL FOR A SPARK PLUG.

APPLICATION FILED DEC-22. I913.

PatentedSept. 7, 1915.

2 SHEETS-SHEET 2.

.3 Wi /memes UNITED STATES PATENT OFFICE.

WILLIAM E. SHERBONDY, OF CLEVELAND, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE BIGSBY ROTARY MANUFACTURING COMPANY, OF CLEVELAND, OHIO, A

CORPORATION OF OHIO.

METHOD OF FORMING A SHELL FOR A SPARK-PLUG.

Specification of Letters Patent.

Patented Sept. 7, 1915.

' Application filed December 22, 1913. Serial No. 808,222.

To all whom it may concern Be it known that I, WILLIAM E. SHER- BONDY, a citizen of the United States, and resident of Cleveland, in the county of Cuyahoga and State of Ohio, haveinvented a certain new and useful Improvement 1n Method of Forming a Shell for a Spark- Plug, of which I hereby declare the following to be a full, clear, and exact description, such as will enable others'skilled in the art to which it appertains to make and use the same.

The objects of the invention are to provide a'novel method of forming a spark plug for an explosion engine from sheet metal, with dies,- whereby said shells can be manufactured with greater speed and economy of labor than the metal shells previously manufactured.

A smooth, serviceable and integral body or shell for the plug is also manufactured by the improved method, requiring practically no labor in finishing and polishing the same.

Heretofore such shells have been formed of bar stock and required to be finished in a lathe or automatic screw cutting machine to trim them to finished size and shape.

By the improved method a smooth finished article is obtained of perfect shape, with an amount of speed and efliciency not attainable by means of any other method.

The invention includes also the forming of a sheet metal sleeve nut which enters the upper end of the shell.

The invention comprises a sheet metal shell formed from acircular blank and open at both ends and having an integral sparking finger or terminal at the lower end and a hexagonal upper end, and a cylindrical or slightly tapered body portion. The body portion is externally screw threaded and the hexagonal portion is internally screw threaded for the insertion and adjustment of the sheet metal sleeve.

The invention further includes the method of progressively modifying and forming the shell from the circular blank, forming the hexagon thereon at one end and forming a closed and rounded lower extremity, and thereafter removing a portion of the extremity to leave a projecting finger and afterward shaping the finger desired.

The invention and the various steps employed in producing the device are hereinafter further descrlbed, shown in the accompanying drawings and clearly pointed out.

in the claims. In the accompanying drawings Figure 1 1s a side elevation of a spark plug showing a sheet metal shell and sleeve therefor; F g. 2 1s a longitudinal section thereof; Fig. 2* 1s a plan view of the shell; Fig. 2 1s a vertical section showing a modified shell employed without a sleeve; Fig. 2 is an elevation of a straight sided shell; Fig. 3 1s a verticalsection showing dies for cutting the blank from which the shell is made; Fig. 4 is a similar section showing the dies which form the blank into a shallow cup shape; Fig. 5 is a similar section showing the dies which still further elongate the cup to approximately the shape of the shell; Fig. 6 1s a similar section showing the dies for reducing the lower end of the shell in cylindrical form; Fig. 7 is a similar view of dies which compress and form a hexagonal exterior upon the enlarged portion of the shell; Fig. 7 is a plan view of this die; Fig. 8 is a similar section showing the dies for cutting away a segmental part of the rounded and closed extremity of the shell to form an integral finger; Fig. 9 is a plan view of this die; Fig. 10 is a plan view of the punch or follower; Fig. 11 is a vertical section of the punch and die employed to give a final shape to the sparking finger; Fig. 12 is a similar sectionshowing forms of dies employed to cut out the first disk or blank and to shape it into cupped form at one operation; Figs. 13 and 14 are plan and edge views respectively of a blank from which the small sleeve nut is formed and Figs. 15, 16, 17, 18, 19 and 20 are plan and vertical sections respectively of the several steps taken in cupping the blank and forming a hexagonal flange at one end and a central opening in the other end. I

In these views A and B are the cylindrical punch and corresponding die by means of which the disk shaped blank G is cut out the shell at I and reduce the diameter f 4 thereof. J is a guide which supports the shell.

cup temporarily. K and L are the punch and die respectively which still further reduce the body or lower portion of the shell and form the closed end, thus leaving an en larged cylindrical upper en M is a guide for the upper end of the N and 0 represent the punch and die which form the hexagon upon the upper or larger end of the shell and are so shaped that a shoulder P compressesthe meta to fill the angles of the die at m, m, and also slightlv reduces the diameterof the cylinder to form the sides of the hexagon at n, n.

The die and punch have each of them cylindrical and hexagonal portions. The closed extremity of the shell is already formed but makes contact with the recessed end of the plug Q, which can'be driven in to remove the finished shell.

In Fig. 8 the punch w and die 3/ are so arranged as to remove a segmental portion of the cupped end of the shell leaving a projecting integral finger or electrode T. To accomplish this the punch a; is provided with a wedge shaped groove m shown in Fig. 10 and the die with a corresponding tongue y.

In Fig. 11 the final stage of the mechanical process is shown where a punch and die .10 and 3 compress the extremity of the finger and reduce the thickness of the metal. The die is provided with a rounded shoulder :2 and the die with a corresponding recess in the tongue.

In Fig. 6 the shoulder Z is provided upon which the porcelain insulator S rests and the dies and punches thereafter retain this shoulder and expand the upper portion to fill the corners of the octagon so as to produce an exterior shoulder R which prevents inserting the plug too'far into the engine cylinder.

In Fig. 6 the lower end of the shell is somewhat tapered to adapt it to a pipe thread with the use of which a shoulder will be unnecessary, but when the lower portion of the shell is perfectly straight as shown in Fig. 2 a washer W is employed to provide a suitablebearing for the shell.

In Fig. 2 a modified form is shown where the sleeve is dispensed with and the upper edge of the shell is turned over the shoulder on the porcelain S at R.

In Fig. 12 a die U and punch V out out .the disk C from the sheet metal plate G and a lower punch V and upper die V in tlliiekpunch V gives the cupped form to the s In Figs. 13 to 20 inclusive the various shapes produced in a disk 0 are shown to produce a finished sleeve (1.. Here a. is the cupped form and a is a cylindrical flanged orm-from which the hexagonal form is produced and the bottom cut out.

Having described the invention what I claim as new and desire to secure by Letters Patent is:

1. An improved method of'forming a shell for a spark plug with dies consisting in first cutting a disk from sheetrmetal, then reducing it to a cupped form, thn elongating the cupped form and reducing its diameter and retaininga curved and closed bottom thereon, still further reducing the diameter of the lower portion of theshell while retaining the size and. shape of the upper portion and producing shoulders simultaneously on the interior and exterior surfaces, compressing the upper portion to form alternate sides and angles of a hexagon thereon, and to give a taper to the lower portion thereof, then shearing away a segmental portion of the rounded bottom of the shell to produce a downwardly and inwardly turned finger, and finally compressing and shaping said finger and producing an external screw thread upon the tapered portion, and an internal screw thread upon the hexagonal portion.

2. An improved method of forming a shell for a spark plug with dies consisting in first cutting a disk from sheet metal, cupping the disk, elongating the same with a curved integral bottom, reducing the diameter of the lower portion thereof, and forming internal and external shoulders, compressing the upper portion to produce an external hexagon thereon, and shearing a segmental portion from the closed bottom to produce an inwardly and downwardly exiiildll'lg finger thereon, and shaping said ger.

3. An improved method of forming a shell for a spark plug with dies, consisting in first cutting a disk from sheet metal, drawing the disk into cup form, elongating the cupped disk, and reducing it in diameter, reducing the diameter of the lower portion, and forming interior and exterior shoulders thereon, next compressing the upper POItlQLI IlII- a hexagonal die to form alternate straight sides andangles thereon, and then cutting away a portion of the curved bottom to form an integral finger or electrode, producing a sleeve having a hexagonal rim, and screw threading the sleeve and interior of the hexagonal portion and the exterior of the lower portion of the shell, substantially as described.

An improved method of forming a shell for a spark plug with dies', consisting in first cutting a disk from sheet metal, drawing the disk into cup form,lelongating the cupped disk and reducing it in diameter, reducing the diameter of the lower portion compressing the upper portion in a hexagonal die to form the exterior of the shell and next cutting away a portion of the curved bottom to form an integral electrode, and then depressing the end of. the finger and shaping vthe same.

5. The method for forming a spark plug which consists in cutting a disk from sheet metal, modifying the shape of said disk to a cup-like form, making a cut in the edge of said cup-like form to partially separate a finger from the remainder of the material, and changing the position of said finger into such relation with the remainder of the material that it may serve as an electrode.

In testimony whereof, I hereunto set my nand this 4th day of December, 1913.

WILLIAM E. SHERBONDY.

In presence ,of

WM. J. KLoTzBAoH, WM. M. MUNROE. 

